Towards an understanding of the Of?p star HD 191612: optical spectroscopy
Abstract
We present extensive optical spectroscopy of the early-type magnetic star HD 191612 (O6.5f?pe-O8fp). The Balmer and He I lines show strongly variable emission which is highly reproducible on a well-determined 538-d period. He II absorptions and metal lines (including many selective emission lines but excluding He IIλ4686 Å emission) are essentially constant in line strength, but are variable in velocity, establishing a double-lined binary orbit with Porb= 1542 d, e= 0.45. We conduct a model-atmosphere analysis of the spectrum, and find that the system is consistent with a ~O8 giant with a ~B1 main-sequence secondary. Since the periodic 538-d changes are unrelated to orbital motion, rotational modulation of a magnetically constrained plasma is strongly favoured as the most likely underlying 'clock'. An upper limit on the equatorial rotation is consistent with this hypothesis, but is too weak to provide a strong constraint.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 2007
- DOI:
- 10.1111/j.1365-2966.2007.12178.x
- arXiv:
- arXiv:0707.0594
- Bibcode:
- 2007MNRAS.381..433H
- Keywords:
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- Astrophysics
- E-Print:
- Accepted for MNRAS